The Lost World of Cessaniti: palaeogeographic relevance of a Late Miocene mammal assemblage from the Central Mediterranean area.

Data from the late Miocene site of Cessaniti (Vibo Valentia, Calabria, southern Italy) suggest the existence of a land connected to Africa in the central Mediterranean.

Although the site has been known since the XIX century for the abundant and well-preserved fossil echinoids of Clypeaster, in the last 20 years, Cessaniti released not only abundant remains of the Sirenian Metaxytherium serresii and rare Cetaceans (Odontocetes: Physiteroidea indet.; Mysticetes: Heterocetus cf. guiscardii) but also a consistent record of terrestrial mammals (Stegotetrabelodon syrticus, Bohlinia attica, Samotherium boissier, Tragoportax cf. rugosifrons,  ‘Ceratotherium’ advenientis, an undetermined Anthracotherid).

The stratigraphic succession outcropping at Cessaniti – “Gentile” Quarry, overlying in unconformity the Paleozoic crystalline basement, is made up of four informal units indicating a transgression from lagoonal to deep-sea environments, dated between 8.1  Ma (Chron C4n) and 7.2 Ma (nannoplankton zone CNM17). The main part of terrestrial mammals comes from the upper part of the shallow sea deposits, locally named “Clypeaster sandstones”, where almost two temporary falls in sea level, probably controlled by tectonics, are testified by the occurrence of soils and fluvial deposits. Only Stegotetrabelodon is also recorded in the underlying lagoonal deposits. The main part of the fossils was collected during quarry works by amateur palaeontologists who summarily recorded their findings. However, they notated the provenance from the upper part of the “Clypeaster sandstones” and noticed the presence of poorly preserved, oxidated echinoids. These letters are typical of the intercalated soils and fluviatile deposits, so the presence of bone beds in fluviatile deposits may be supposed.

The terrestrial mammal association has no insular adaptations nor relationships with the islands of central Italy (Tusco-Sardinian and Apulo-Abruzzi bioprovinces).  The occurrence of Stegotetrabeolodon syrticus represents the only “out of Africa and Arabia” record for the species and has plesiomorphic characters, coherent with an early arrival at Cessaniti. Giraffids suggest a westward expansion of the Pikermian biome from the Greco-Iranian  bioprovince through North Africa (where scanty remains are recorded) and then to Cessaniti. Tragoportax was widely spread in Eurasia and Africa. The new species‘Ceratotherium’ adenitis can be related to African Rhinocerontidae. The palaeoecology of the mammal association indicates a mosaic environment with open spaces, probably similar to the modern savannah but less arid, similar to that suggested for the Pikermian biome.

The stratigraphic and taphonomic data, the abundant record of the terrestrial mammals, and their palaeoecology and taxonomy support the hypothesis of a land in terrestrial continuity with North Africa. Therefore, the accumulation of floating carcasses coming from north Africa can be excluded.